1. Field of Invention
The invention relates to an ink-jet recording apparatus, and more particularly, an ink-jet recording apparatus of ink tube supply type wherein generation of air bubbles in an ink tube is restricted to maintain excellent printing quality.
2. Description of Related Art
An ink-jet recording apparatus of an ink tube supply type supplies ink to a recording head via an ink tube from an ink tank. In the ink-jet recording apparatus of this type, one end of the ink tube is connected with the ink tank provided separately from a carriage, and the other end is connected with the recording head mounted on the carriage. Thus, the recording head and the ink tank are connected with each other via the ink tube. Ink stored in the ink tank is supplied to the recording head via the ink tube. The ink tank connected with one end of the ink tube is fixedly provided. The recording head connected with the other end of the ink tube is mounted on the carriage and reciprocates in a main scanning direction. Accordingly, the ink tube requires flexibility and durability to bending/warping. In order to satisfy such requirements, the ink tube is made of olefin rubber, such as ethylene rubber and butadiene rubber.
Generally, a negative pressure is applied to the ink to be supplied to the recording head, so that air is likely to get into the ink through walls of the ink tank and the ink tube because of pressure difference between inside and outside of the ink tank and the ink tube. In particular, because the ink tube is made of the olefin rubber, the ink tube has air-permeability. This characteristic allows air to get into the ink through the wall of the ink tube to generate air bubbles in the ink tube. The air bubbles generated in the ink tube are conveyed to the recording head with contained in the ink, and the air bubbles may close an ink flow path or ink nozzle. This may cause non-ejection of the ink or deterioration of the printing quality.
The invention provides an ink-jet recording apparatus, wherein generation of air bubbles in an ink tube is restricted to maintain excellent printing quality.
According to one aspect of the invention, an ink-jet recording apparatus includes a recording head that ejects ink, an ink tank that is provided separately from the recording head and stores the ink therein, an ink tube that supplies the ink from the ink tank to the recording head, a member that provides an enclosed space, extending along at least a portion of the ink tube, and a pressure reducing device that reduces pressure in the enclosed space.
In the ink-jet recording apparatus described above, the ink stored in the ink tank is supplied to the recording head through the ink tube. The ink tube is provided with the enclosed space by the member which extends along at least one portion of the ink tube. The pressure of the enclosed space is reduced by the pressure reducing device. Thus, air contained in the ink is sucked into the enclosed space, in which the pressure is reduced. With this structure, generation of air bubbles in the ink tube is restricted.
In another aspect of the invention, an ink-jet recording apparatus includes a recording head that ejects ink, an ink tank that stores the ink, and an ink tube coupled between the recording head and the ink tank to supply the ink from the ink tank to the recording head. An air discharge member extends along the ink tube and is connected to a vacuum source that reduces pressure in the air discharge member to reduce air bubbles in the ink contained in the ink tube.
In another aspect of the invention, an ink-jet recording apparatus includes an ink tank that stores ink, a recording head that ejects the ink and is provided separately from the ink tank, and an ink tube coupled between the recording head and the ink tank to supply the ink from the ink tank to the recording head. An air discharge tube extending along the ink tube and having an air permeable wall is provided. Also, a vacuum source is connected to the air discharge tube to reduce the pressure therein to draw air bubbles present in the ink in the ink tube through the air permeable wall.
In yet another aspect of the invention, a method of supplying ink to a recording head is provided. The method includes providing an ink tube that connects an ink tank that stored ink to a recording head that ejects the ink, and placing an air discharge member that extends along the ink tube. The pressure in the air discharge member is lowered to reduce air bubbles in the ink contained in the ink tube.